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Q. Do solar panels really work in Washington?

A. Yes, they do! While the output is lower in cloudy or rainy weather, solar cells still generate useful power under these conditions.

How do they work, exactly?

Solar panels consist of individual solar cells, connected together, that convert sunlight into electricity through what is called the photovoltaic effect, or PV. Solar cells absorb photons (light), which creates electrons.

The electrons are directed out of the cells to create an electrical current. This current is in the form of a direct current, or DC, which is then converted into an alternate current, or AC, that your building can use.

The panels are constructed with an aluminum frame, a polymer laminate sheet to encapsulate the cells, a backing material and a glass cover.

The average size of a panel for residential rooftop applications is about 15 square feet and will weigh approximately 35 pounds.

Most panels are rated for snow and wind loads of 100 pounds per square feet and 50 pounds per square feet respectively.

During a site survey, a qualified solar PV installer or designer will look at the roof to make sure it is in good condition with no leaks or damage, but roofs do not need to be new to accommodate solar panels.

Aluminum mounting hardware and rails are mounted on the roof and fastened by stainless screws into trusses. The solar panels are mounted on the rails, allowing for airflow between the roof and the solar array.

Panels are installed by certified electricians who must obtain the necessary permits, install safety equipment, affix safety labeling and provide a diagram for your power company and for your records.

Depending on the size of your solar array, a structural engineer may be necessary to ensure that your roof can handle the additional weight.

Most solar panels come with a 25-year linear warranty, meaning they will last about as long as a 25-year roof, but many outlast that and the panels themselves can be dismounted and remounted for roof repairs should the need arise.

A measurement of your roof will let you know how many solar panels will fit on it, but determining how many panels your house would require is done by determining the number of kilowatt hours of electricity the home uses on a daily average throughout the year.

For an existing home you can figure this out from one year’s worth of power bills or by contacting your power company.

With a new home there is no usage history, but a family moving into a new home could look at their past usage history for a rough idea.

Even if your home and your neighbor’s home are the same size and floor plan, the usage could be very different depending on lifestyle and the number of family members living in the home.

If the prospect of lowering or eliminating your energy bill has you thinking about solar panels, you’ll be glad to know that Washington state has one of the best solar-energy incentive programs in the country. You can find out more at

Pascal Jean-Baptiste, president of Revosol Solar Energy, is a member of the Master Builders Association of King and Snohomish Counties’ Remodelers Council and provided the information contained in this article. If you would like more information or have questions about home improvement send them to Sorry, no personal replies. Always consult local codes and contractors.